The MPR web site http://mpr.nci.nih.gov contains information about human phosphorylation sites against which there are commercially available phospho-antibodies. The tool continues to be frequently used by scientists around the world. For example, it has been used from over 5000 ip addresses around the world. We have continued to add antibodies periodically.The user can gain access to the information in MPR in several ways: by browsing a list of all proteins for which phospho-antibodies are available; by searching for sites on an individual protein, or by browsing lists of phospho-antibodies from any particular company. Information provided for a site includes the exact sequence of surrounding residues (which is critical to unambiguous identification of the site of interest), a list of antibodies available against that site, several critical parameters for those antibodies, direct links to the supplier's web site information on each antibody; and links to pubmed citations related to that site. MPR also provides links to other web pages for each gene/protein that facilitates user exploration of resources including Genbank, Locuslink, CGAP, and Symatlas pertinent to their studies. Additional functionality provided is the ability to search for a site (and antibodies) based on the sequence of that site. Not only does that allow rapid/easy retrieval of the site information on that site, it also allows the user to survey sites of similar sequence that may be observed as cross-reactions or may have functional similarities. In addition, MPR now provides a curated collection of links that directs users to other particularly informative web cites relevant to protein phosphorylation.The tool we have developed for scanning proteins for PKC sites also continues to be used by many scientists. We have improved formatting and infrastructure that will facilitate future enhancements. The infrastructure we have developed for MPR has continued to facilitate our role in organizing information on phosphorylation sites for the CCR/BD collaboration. In addition, we have now constructed a prototype web-based version of KBTool, a knowledgebase program that we have been using internally for several years. We will begin testing it with a small group of external users.